1. Field of the Invention
The present invention relates to a taking lens apparatus, and particularly to a taking lens apparatus that optically takes in an image of a subject through an optical system and that outputs the image as an electric signal by means of an image-sensing device (i.e. a taking lens apparatus for use as the principal component of a digital camera, video camera, or camera built in or externally fitted to a personal computer, mobile computer, portable telephone, personal digital assistant (PDA), or the like), and more particularly to a taking lens apparatus provided with a compact high-zoom-ratio zoom lens system.
2. Description of the Prior Art
In recent years, as personal computers become more and more popular, digital still cameras, which permit easy acquisition of images, have been becoming increasingly popular. As digital still cameras become more and more popular, models offering increasingly high zoom ratios are sought after, and accordingly there is a growing demand for increasingly compact and high-zoom-ratio taking lens systems. On the other hand, as image-sensing devices with more and more pixels are developed, increasingly high-performance taking lens systems are sought after.
However, no known conventional zoom lens system satisfactorily meets these conflicting requirements of compactness and a high zoom ratio combined with high optical performance.
An object of the present invention is to provide a taking lens apparatus provided with a compact, high-zoom-ratio, but nevertheless high-performance zoom lens system.
To achieve the above object, according to one aspect of the present invention, a taking lens apparatus is provided with: a zoom lens system for focusing the light from an object so as to form an optical image; and an image-sensing device for converting the optical image formed by the zoom lens system into an electric signal. Here, the zoom lens system is provided with, from the object side: a first lens unit having a positive optical power and composed of three or fewer lens elements in total including at least one negative lens element and at least one positive lens element; a second lens unit having a negative optical power and moving, during zooming, in such a way as to be located always on the image-plane side of the position in which the second lens unit is located in the shortest-focal-length condition; and one or more succeeding lens units. This zoom lens system permits the magnification to be varied by varying the distances between the lens units, and fulfills the following conditions:
0.92 less than FW/IH less than 1.85;
ND less than 1.53; and
VD greater than 78,
where FW represents the focal length of the zoom lens system in the shortest-focal-length condition; IH represents the maximum image height; ND represents the refractive index for the d line of the positive lens element mentioned above as at least one included in the first lens unit; and VD represents the Abbe number for the d line of the positive lens element mentioned above as at least one included in the first lens unit.
According to another aspect of the present invention, a taking lens apparatus is provided with: a zoom lens system for focusing the light from an object so as to form an optical image; an image-sensing device for converting the optical image formed by the zoom lens system into an electric signal; and an optical low-pass filter, disposed in the optical path on the object side of the image-sensing device, for optically controlling a predetermined spatial frequency component included in the optical image formed by the zoom lens system. Here, the zoom lens system is provided with, from the object side: a first lens unit having a positive optical power and composed of three or fewer lens elements in total including at least one negative lens element and at least one positive lens element; a second lens unit having a negative optical power and moving, during zooming, in such a way as to be located always on the image-plane side of the position in which the second lens unit is located in the shortest-focal-length condition; and one or more succeeding lens units. This zoom lens system permits the magnification to be varied by varying the distances between those lens units, and fulfills the following conditions:
0.92 less than FW/IH less than 1.85;
ND less than 1.53; and
VD greater than 78,
where FW represents the focal length of the zoom lens system in the shortest-focal-length condition; IH represents the maximum image height; ND represents the refractive index for the d line of the positive lens element mentioned above as at least one included in the first lens unit; and VI) represents the Abbe number for the d line of the positive lens element mentioned above as at least one included in the first lens unit.